Tap starter



July 16, 1935. v M, CROSS I 2,008,436

TAP STARTER Filed April 29, 1935 \nvenToT. Grgsvenor NLCross /mwzw 1 AHys.

Patented July 16, 1935 UNITED STATES 1 'This invention relates to a device for guiding and insuring the correct position of a screw thread cutting tap or similar tool when startingits operation-in apreviously formed hole. Such a tap must be held in accurate alignment with the hole in-the work because if the tapis started-in an angular directionit will bind, cut thQthIBHdiHl-r perfectly, and if, after it is started in the work, itbe forced back into aligned position, it may be damaged or broken and the work injured.

The object of the present invention is to providea simple construction which will surely and accurately guide the tap or similar tool in the startingof the work, maintaining it in aligned position with the hole in thework.v v r The object of the invention is to provide such a device which shall be of a universalcharacter, sturdy, practically indestructible, having no movable parts to get out'of order, inexpensive in construction, capable of use with a large range of 'tap' sizes, and capable of use upon work presenti'ng'either a flat surfaceor a curved orangular surface.

These and other'objects and features of the invention will appear more fully from the accom- -panyingdescription and drawing and will be particularly pointed ofit'in the claims.

The drawing illustrates preferred forms ofconstruction embodying the invention in which:

Fig lis a top plan view of one formof such construction.

Fig. 2 isa bottom plan view of the construction shown-in Fig. 1. V

Fig. 3 is a side elevation of the construction shown in Fig. 1. V V

Fig. 4 is a cross section taken, on the line i -4 of Fig. 1. V

Fig. 5 is an end elevation of another form.

Fig. 6 is a; plan view of the construction shown in Fig. 5. y

A device embodying the invention is in the form of a block made of any suitable, rigid, hard material. The construction is such that the en tire device may be made, for example, of metal by a die casting operation "and may; be desirably finished with chromium plating.

The block of this inventionmay'beof various shapes, the simplest and preferred examples of which are illustrated. The essentialfeatures' of the broad construction are that it must present positioning means'to rest upon and position it with respect to a fiat work-piece, that it must present a plurality of rectilinear V-shaped positioning grooves extending across the block in which cylindrical work-pieces may be seated and thus the block be positioned with respectto the axes ofsuch cylindrical work-pieces, that there 7 shall be a plurality of tap-guiding cylindricalbores extending through the block' each withltsiaizis normalto, and intersecting the apex of, .andbi 5 "secting the angle of, one of the Vshaped grooves and with thediameters of thebores correspond ing respectively'to the diameters of'ajplurality of taps, so that the axisof each bore will benormal to thefiatsurfaceof awork-piecelpositioned'by lo the block and normal to the axis of a cyli'ndrica'l work-piece positioned bya groove, and that. the block sh'all be of suflicientdepth or thickness properly'to support the taps as they are guided into the work-piece. g C 15 In the construction illustrated in Fi'gs..1' to:4, the block' is of 'i fiat" cylindrical shape presenting the flat bottom positioning surface I; Three rectilinear V-shapedsymmetrical positioning grooves, that is, grooves each or. which hasgits two 5 faces ofsequal and uniform depth throughout; 2,

'3; and '4 extend, in this case transversely: and diametrically, across theblockand upward'fromthe bottom surface. The block is preferably lightened iniweight and the materialfthereof. reduced 25 by. acentral depression 5 at theitop, .a centraldepressi'omfi at the bottom and by'symmetri'eal V-'- shaped recesses: 1 extending downward from" the top and inward from thesides: leaving at'the top of the block the'ribs '8' above the V-shapedposie tioningrgroovesl V l The 1 fiat bottom 1 positioning surface is": defined by theuedges of. the V-shaped grooves and, while the bottom depression 6 and the V-shaped grooves themselvesremove aylargeportion of the bottom 35 surface; extensive sections are left so thatthe blOCkTWhGH placedupon the fiat surface'is accurately positioned thereon by this surface of which the. edges of the grooves are elements. t

Whentheblock is toi be used with cylindrical 40 work piec'es such as rods'orbars, it is placed with one of" the transverse V-shaped grooves resting over the rod or bar and thus again the blockis accurately positioned and supported with respect to the surface offthe'rod or ban ItWill-now be seen that alarge numberjof -ta'p guiding bores-may be formedin' the block e ahh one of which can'have the same relation to the flat work-piece positioning element and to' 'one or the grooves thus enabling a' wide range of tap' siaes to be guided' by the'use of" a' single block embodying the invention. These cylindrical bores are formed in the block and extend entirely therethrough each with its axis normal to the bottom positioning surface I or the surface 66 defined by the groove edges and each with its axis intersecting the apex of one of the V-shaped grooves. In the construction illustrated. the

' block is formed to be used for guiding screw thread cutting taps for A. S. M. E. standard machine screw sizes 2, 3, 4, 5, 6, 8, 10, 12, 3", but it is obvious that the number of sizes and the particular diameters may be varied as required. In the present construction the large size, is at thecenter of the block while the other sizes are distributed in the ribs 8. In the case of the larger sizes the cylindrical bores such as 9 are of the same size throughout the block, While in the .in sucha block in a'hole in a piece of work whether'the work be flat or of other shape, the block is positioned on the work with its flat bot.- tom, positioning surface engaging the surface of thenwork, if'the work be flat, or with the proper .V-shaped grooye'engaging the work, if the work :bea rod or bar, for example, andin each case the proper cylindrical bore is readily held in accurate alignment with the axis of the hole in the work; The tap is then inserted in the bore and its correct'positi-on insured while being operated until it has well started in the work when it and the block may be removed and the operation completed 1 Y The: same principles are embodied in 'the'con- 'structions shown in Figs. 5 and6.

In this form the blockis of a general polygonal shape and the 'V-sh'aped'positioning grooves II, I2 and I3 extend longitudinally of the block inward from the sides of the block; Each of these positioning grooves'having its two faces of equal and uniform depth throughout therefore presents parallel fedges I I for the groove :I I, I5 for the groove I2, and I6 for the groove I 3, adapted to rest upon and position the flat surface of a work-piece while a'cylindrical work-piece may be seated in and positioned'by each groove. .The parallel edges of the grooves are preferably extended into plane surfaces such as 20 normal to the axes of the bores thus to give a widerseat for the block on,

the fiat surface of the work-piece. The block is preferably reduced 'by'the V-shaped grooves I'I, I8 and I9 to renderthe block symmetrical and lighten the construction; I ,The'plurality of cylindrical bores of the type already described for guiding the taps of the different sizes are shown with the corresponding tap s zes. Each-of these cylindrical bores extends through the blo'ck'and has its axis normal to, and intersecting the apex of, and bisecting the angle of, one of the V-shaped grooves II, I2 or I3.-

Thus it will be seen that this construction shown in Figs. 5 and 6, when positioned either upon the flat surface. of a work-piece or upon a cylindrical workpiece, ensures the accurate starting of either size of-tap into the work.

The block may also be used for guiding a drill in drilling a hole such, for example, as is subsequently to be tapped and for this purpose one of attain the bores of a smaller size than the tap may be employed or separate bores may be formed in the block for that purpose.

There is thus presented a very simple, inexpensive, eflicient device of a universal character capable of handling a wide range of sizes of taps or similar tools and ensuring the accurate location and starting of the tap in work of various characters.

Having thus described the invention, what is claimed as new, and desired to be secured by Letters Patent, is:

- 1. A tap starter comprising a rigid, hard block having a plurality of rectilinear V-shaped positioning grooves extending across the block with the two faces of each groove of equal and uniform depth throughout and a pluralityof cylindrical bores of different diameters extending through the block, each with its axis normal to, intersecting the apex of, and bisecting the angle of, one of the, V-shaped grooves and with the diameters of the borescorresponding respectively to, the diameters of a plurality of taps of different sizes to cause the axis'of each bore to'be normal to the flat surface of a work-piece positionedjby the edges of its groove and normal to the axis of a cylindrical work-piece seated in and positioned by its groove. 7 w p 2. A tap starter comprising a rigid, hard, polygonal block having a plurality of parallel V- shaped positioning grooves extending longitudinally of the block and inward from thesides of the block with the two faces of each grooveof equal and uniformdepth throughout and a plurality of cylindrical bores of different diameters extending through the block each with its. axis normalto, intersecting the apex of and bisecting the angle of, one of the. V-shapedgrooves and with the diameters of the borescorresporidi'ng re spe ctively to the diameters of a plurality of taps of, different sizes to cause the axis of each bore to be normal to the flat surface of a work-piece positioned by the edges of its groove and normal to the axis of a cylindrical work-piece seated in and positioned by its groove. v p

3. Atap starter comprising arigid hard block having a flat bottom positioning surface, aplugrooves extending transversely across the block and upward from thebottcm positioningsurfae,

shaped symmetrical positioning grooves extending upward from the bottom Ipositioning surface,

and a plurality of cylindrical bores-of .different diameters extending through the block, each with its axisnormal to the bottorn positioning surface and intersecting the apex ofone of the V-shaped grooves-and withthe-di'ameters of the bores corresponding respectively to the diametersof -a pluralityof taps of differen-tsizes..

GRosvENoai/i. c aoss. L.

rality of v -shaped. symmetrical positioning 7 

